Weighting Is The Hardest Part

Tips on camper/towing weight

Trailer weight terms and numbers can be rather confusing--which numbers are most important? How much weight can my tow vehicle actually pull? Why do some of the largest/heaviest campers have the least cargo capacity?

This page sorts through the confusion so you can be confident of the weight you're able to tow safely.

GVWR and Dry Weight

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GVWR stands for "Gross Vehicle Weight Rating" and is the total combined weight of a trailer plus all of the cargo it could theoretically hold. This number is generally derived from the total weight that each of the tires can hold (their rating) plus the weight of a trailer that's carried by the hitch (tongue weight/ hitch weight).

GVWR is based on the load capacity of a trailer's tires and is independent from the actual weight of the trailer.

Example: the T-series uses 13" tires on a single axle. The 13" tires are rated to hold 1500 lbs each (3000 lbs. total). The tongue weight for the T-series averages 270 lbs. So the GVWR of most T-series campers is 3270 lbs. This is the total weight the trailer could hold, but it can only get to that weight if you put a lot of stuff in the trailer because the actual weight of the trailer is much less.

The actual weight of the trailer is called the dry weight. Dry weight is the total weight of the trailer before adding cargo. This includes the true weight of the trailer supported by the tires and the hitch.

axle weight + tongue weight = dry weight

Why we use dry weight

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Let's say your vehicle is rated to pull 3500 lbs. In the T-series example the GVWR is 3270 lbs. --according to the numbers your vehicle can pull the T-series camper*.

Now suppose you upgrade the 13" tires to 14" tires. Flagstaff's 14" tires are rated at 1750 lbs. so the GVWR increases to 3770 lbs. Now it appears the T-series is too heavy for your vehicle. The actual weight (dry weight) of the trailer, though,increased by only ~20 lbs. (the 14" tires and wheels are slightly heavier than the original 13" tires).

Another example: since the GVWR is based on tire capacity let's see what happens when we use the same tires on several differently sized trailers. Suppose we have an 8' trailer that weighs 1000 lbs. at the axle, a 12' trailer that weights 2000 lbs., and a 16' trailer that weights 3000 lbs. We use the same tires for all three trailers and the tires have a load capacity of 1500 lbs. each. We balance the trailers to have the same tongue weight, 300 lbs.

Technically these three trailers have the same GVWR (3300 lbs.) but clearly the 1300 lb trailer will be easier to pull than a 3300 lb. trailer. In fact, some vehicles that could not pull the 3300 lb. trailer safely maybe could pull the 1300 and 2300 lb. trailers. If GVWR alone was used two perfectly viable trailers may have been dropped from contention.

Bottom line: focus on dry weight first.

Cargo Capacity

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Cargo capacity is simply the GVWR minus the dry weight of the trailer. It is not a measurement of the storage space inside a camper. Some campers have a high cargo capacity but not enough storage areas to pack that much weight into the camper (unless you're packing gold or lead bars into the camper). Cargo capacity only relates to the weight the tires can hold after the weight of the trailer has been accounted for.

That is why some of the largest trailers also appear to have the least amount of storage space. Actually, the larger trailers have plenty of storage space but the weight limit for filling up that space is decreased because the camper itself weighs more than the smaller campers; more of the tire's load limit is already taken up by the dry weight of the trailer.

The average dry weight of a T-series camper is 1900 lbs. From the example above we know the GVWR for a T-series averages 3270 lbs. So, the average T-series camper can hold ~1370 lbs. of cargo.

Note about water, propane, and batteries

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Dry weight does not include water, propane, or a battery so that must be accounted for in the cargo weight. For most Flagstaff trailers the cold water storage is 20 gallons. In many Flagstaff trailers a hot water package is available which adds 6 gallons of water. Water weighs 8.6lbs. per gallon. So fully loaded, the water in a hot water system weighs over 220 lbs.

An empty 20# propane tank usually weighs about 17 lbs. A full 20# tank holds 20 lbs. of propane, obviously. So each propane tank adds 37 lbs. to the weight of the trailer.

A Group 27 battery (like the kind we install on our campers) weighs 53 lbs.

weight of "wet" items

The total weight for water, propane, and battery on a typical Flagstaff pop-up (with no hot water) is 262 lbs. Keep in mind, though, that some people wait until they are at their campsite (or at the last gas station they come to before heading to their campsite) before filling the water tank so they don't have to travel with that extra weight.

Of course if your campsite has water and power hook-ups you can leave the tank empty and leave the battery at home to save even more weight.

Tongue Weight

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Tongue weight is the weight carried by the hitch of the tow vehicle. In our T-series example even though the total weight of the trailer is 1900 lbs. only 1630 lbs. is supported by the axle/tires. The other 270 lbs. is supported by the hitch.

A general rule of thumb is that 10% of the total weight (dry weight) of a trailer should be on the tongue. This keeps the trailer stable during towing because the trailer is partially dependent on the tow vehicle for direction.

In fact, the more weight on the tongue the more dependent the trailer is on the tow vehicle (too much tongue weight, though, puts excess stress on the hitch and tow vehicle's suspension). Too little tongue weight leaves a trailer unstable and able to sway from side-to-side while in motion (this is called "fish-tailing").

Flagstaff trailers are generally built slightly tongue-heavy to keep the trailer completely stable. Flagstaff trailers are among the easiest trailers to tow for this reason.

Altitude Adjustment (important in Colorado!)

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Please note that a vehicle's towing capacity is rated at sea level. Higher elevation means thinner air. Since an internal combustion engine breathes air the thinner the air the less power an engine is able to produce.

Graphic showing altitude power loss as explained in following paragraph

In general, for every 1000 ft. increase in altitude above sea level an engine's power decreases around 2-3%**. So if a vehicle's manual says it can tow 3500 lbs. (at sea level) the same vehicle would tow ~3100 lbs. in Denver. Going over Vail Pass (10,662') the engine's towing capacity is down to ~2700 lbs.

Electric Brakes

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In Colorado, if a trailer's GVWR exceeds 3000 lbs. a braking system of some sort must be installed on the trailer. Flagstaff includes electric brakes on almost all of their trailers (LTD series excepted, but brakes can be installed as an option) but a brake controller must be present in the tow vehicle to operate the electric brakes. Brake Controller details

Putting it all together

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Let's say we have a big SUV that could originally tow 3500 lbs. We add a tow package with a transmission cooler to our vehicle that increases the towing capacity to 4000 lbs. Since that number is only for sea level we take off 20% from 4000 and determine that in Colorado's mountains we want to keep the trailer weight under 3200 lbs.

Let's consider the 823D. Even though the 823D's GVWR is 3339 lbs. and goes above our vehicle's tow-weight limit, we know that 3339 lbs. is not the actual weight of the camper. Since the dry weight of the camper is 2445 lbs. we are well below our limit of 3200 lbs.

After we add water, propane, and a battery (310 lbs.) we have about 450 lbs. available for our gear: food, clothes, firewood, chairs, pots & pans, tools (and don't forget a first aid kit).

Because the GVWR is over 3000 lbs. we also have a brake controller added to our tow vehicle and now we're ready to go camping!

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*This statement does not take altitude into account. Altitude considerations are explained above in "Altitude Adjustment" section. ( Back to Why We Use Dry Weight)

**This is a rough measurement that ignores temperature, engine modifications like superchargers, and limits its scope to drivable roads in North America; we're just trying to get a reasonable number for what a vehicle can pull in Colorado. ( Back to Altitude Adjustment)